1. Field of the Invention
The present invention relates to retractable running boards for vehicles.
2. Description of Related Art
Most conventional vehicle running boards have fixed positions relative to the frames of the vehicles to which that they are attached.
Designers of fixed-position running board vehicles must balance ground clearance against the desire to place running boards in a lower, more passenger convenient position midway between ground level and the lower edge of the vehicle door opening. In a vehicle such as a truck, in which a large ground clearance is advantageous, the cab and passenger seats are typically disposed well above ground level. Consequently, conventional running boards provide an intermediate step for passengers to use to enter and exit the vehicle. From the standpoint of facilitating a passenger's entrance and exit from the vehicle, the most convenient height for a running board is generally at about half the distance between the ground level and the lower edge of the vehicle door opening. However, disposing the running board at such a low position reduces the vehicle's ground clearance. Consequently, designers must sacrifice either convenience or ground clearance when determining the height of a fixed-position running board.
In response, certain retractable running boards, such as the running board disclosed in U.S. Pat. No. 5,697,626, include running boards with selectively variable heights. When the vehicle is being driven, the running board is raised vertically to improve the vehicle's ground clearance. Conversely, when the vehicle is stopped, the running board can be lowered to position the running board at a more convenient height for the passengers.
Vehicle designers face an additional dilemma when determining the lateral position of fixed-position running boards. To provide the most convenience to passengers entering or exiting a vehicle, the running board should be disposed laterally outwardly from the vehicle's entrances/doors such that the lower edge of the door opening, the running board, and the ground, form laterally- and vertically-spaced steps like those in building stairways. Unfortunately, disposing a running board fixed laterally outwardly from the vehicle for the passengers' convenience can tend to increase the vehicle's width.
Certain retractable running boards, such as the running board disclosed in U.S. Pat. No. 3,608,957, have been designed to extend laterally outwardly when the vehicle's door is opened such that the running board is in a convenient laterally-outward position when the passengers need to use it to enter and exit the vehicle. Conversely, the running board is retracted laterally inwardly when the door is closed so that the vehicle has a narrower width during operation.